Zoom G5 Pedal Issue

I was wondering whether anyone around here could help me with my problem. It seems that my Zoom G5 processor's pedal is not registering the up-down movements. Left-right are ok, but when calibrating or trying to use a patch tied to it, it is simply not registering the movement at all. This is quite strange since, from what I gather, if the darn thing was broken, it wouldn't work left-right either...